Police have issued a warning against motorists alerting other drivers of approaching checkpoints by flashing their lights.

In a post on the PSNI Foyle Facebook page said it had become aware of cars speeding through the Maghermason and Newbuildings areas of the city, often running through red lights and not stopping for pedestrians.

A spokesperson wrote: "So Waterside NPT (Neighbourhood Policing Team) did a speed op. No detections today, everyone was suspiciously well under the speed limit.

"Maybe that's something to do with drivers flashing their lights at motorists approaching our point.

"If you do wish to flash your lights at motorists to warn them, please remember this offence code: N160. It might speed the issue of your ticket along for the unlawful use of your headlights.

"In the wise words of the terminator, 'I'll be back'."

The N160 is a motoring offence in Northern Ireland for an unlawful use of a car's lights.